1. Field of the Invention
The present application relates to a compressed natural gas injector which is tolerant of contamination in the gas.
2. Description of the Related Art
Compressed natural gas (hereinafter sometimes referred to as xe2x80x9cCNGxe2x80x9d) is becoming a common automotive fuel for commercial fleet vehicles and residential customers. In vehicles, the CNG is delivered to the engine in precise amounts through gas injectors, hereinafter referred to as xe2x80x9cCNG injectorsxe2x80x9d. The CNG injector is required to deliver a precise amount of fuel per injection pulse and maintain this accuracy over the life of the injector. In order to maintain this level of performance for a CNG injector, certain strategies are required to help reduce the effects of contaminants in the fuel and to deliver the fuel to the intake manifold in precise amounts and flow patterns.
In general, fuel injectors require extremely tight tolerances on many of the internal components to accurately meter and deliver the fuel. We have invented a CNG fuel injector which incorporates a novel fuel columnating jet device which assists in precision delivery of the fuel, reduces engine misfire, and improves exhaust emissions.
An electromagnetically operable fuel injector for a gaseous fuel injection system of an internal combustion engine, said injector having a generally longitudinal axis, which comprises, a ferromagnetic core, a magnetic coil at least partially surrounding the ferromagnetic core, an armature magnetically coupled to the magnetic coil and being movably responsive to the magnetic coil, the armature actuating a valve closing element which interacts with a fixed valve seat of a fuel valve and being movable away from the fixed valve seat when the magnetic coil is excited, the fixed valve seat defining a fuel valve aperture. The armature has a generally elongated shape and a generally central opening for axial reception and passage of gaseous fuel from a fuel inlet connector positioned adjacent thereto, the fuel inlet connector and the armature being adapted to permit a first flow path of gaseous fuel between said armature and said magnetic coil as part of a path leading to said fuel valve. At least one fuel jet columnating device is positioned below the fuel valve for receiving fuel flow from the valve aperture in a stream having a first transverse dimension, and for permitting the stream to widen into a funnel shaped section having a transverse dimension greater than the first transverse dimension, and to thereafter columnate stream to a transverse dimension greater than the transverse dimension of the valve aperture.
The fuel inlet connector and the armature are spaced to define a working gap therebetween and are adapted to permit the first flow path of gaseous fuel within said working gap. The valve body is positioned downstream of the armature and has at least one aperture in a wall portion thereof for reception of fuel from at least two of the flow paths of gaseous fuel from the armature and the fuel inlet connector. The fuel injector further comprises a valve body shell at least partially surrounding the armature and the valve body, the valve body shell defining a radial space with the armature for passage of the first flow path of gaseous fuel between the armature and the valve body shell. The fuel inlet connector is positioned above the armature and is spaced from the armature by a working gap, the fuel inlet connector defining a through passage for directing fuel toward the armature and the fixed valve seat.